Nitazoxanide is a 5-nitrotiazol with antibacterial and antiparasitic activity with a broad spectrum action. Its chemical formula is 2-acetolyloxy-N-(5-nitro-2-tiazolyl)benzamide and has the following structure:

The procedure for the synthesis of nitazoxanide and the use thereof were originally disclosed by Rossignol in U.S. Pat. No. 3,950,351. U.S. Pat. No. 5,387,598 discloses nitazoxanide formulations suitable for the treatment of intestinal parasitic infections improved through the use of surfactant excipients and starch. U.S. Pat. No. 5,968,961 discloses nitazoxanide formulations with optimal particle size to achieve the therapeutic effect and reduce the side effects. U.S. Pat. No. 6,117,894 discloses improved nitazoxanide formulations in terms of stability through the use of acidifying excipients. US patent application 20100209505 discloses nitazoxanide compositions in double-coated tablets where one coating is of immediate release and the other coating is a controlled-release coating specifically designed for the treatment of chronic viral hepatitis C.
Nitazoxanide is currently approved in several countries for the treatment of infections caused by parasites in two pharmaceutical forms: immediate-release tablets and powder for immediate release suspension. These formulations require the delivery of 1 intake every 12 hours. Depending on the age of the patient the following dosage schedule and method of administration are used:
AgePosologyTotal daily dose1 to 3 Years100 mg every 12 hours200 mg4 to 11 years200 mg every 12 hours400 mg12 to 15 years300 mg every 12 hours600 mg16 years or more500 mg every 12 hours1000 mg 
The main side effects of nitazoxanide are gastrointestinal, the most frequent ones being: abdominal pain, diarrhea, nausea and vomiting. These effects increase as the dose increases. The gastrointestinal side effects of the known nitazoxanide formulations are very frequent and cause that a significant percentage of patients do not complete the treatment. Partial compliance with the treatment generates recurrence of the infection and increases the likelihood of generating resistance to the drug.
Therefore, there is a need for an improved nitazoxanide formulation for the treatment of parasitic infections that will allow a better tolerance and better compliance with the treatment.
It should be noted that the controlled-release composition in tablets disclosed by Rossignol in US patent application 20100209505 is not adequate for solving the raised problem due to several reasons. The formulation disclosed by Rossignol is specifically designed for the treatment of chronic viral hepatitis C (systemic treatment that requires high nitazoxanide plasma levels). In the aforementioned patent application, the inventor uses high viscosity polymers such as hydroxypropyl-methylcellulose (Methocel) or hydroxypropyl-cellulose (Klucel) that when they hydrate and swell remain longer in the stomach (gastro retention phenomenon). In this way they achieve the gradual release of the active ingredient in the higher absorption area of nitazoxanide (in the stomach and first portion of the gut). The controlled-release tablets disclosed by Rossignol do not achieve a sufficient reduction of the gastrointestinal side effects. As reported in the aforementioned patent application, the most common side effects for the dose of 675 mg. were: Diarrhea 33%, 25% Nausea and abdominal pain 17%.
On the other hand, the controlled-release tablets described by Rossignol containing 675 mg of nitazoxanide are very bulky, they have a weight higher than 1000 mg. This type of tablets is not suitable for pediatric or adult patients with swallowing problems due to its large size.
For these reasons, it was aimed to find a composition that would be able to overcome these drawbacks, which resulted in the present invention. In the present invention, we designed a nitazoxanide composition capable of releasing the active ingredient in pulses in order to distribute the active ingredient throughout the intestinal tract and allow for a better tolerance. We have achieved that the release of nitazoxanide focused to different regions of the digestive system would significantly reduce the side effects of the treatment. After numerous tests, it has been found that the composition of the present invention manages to obtain the desired dissolution profile by combining an immediate release moiety and at least a pH-dependent release moiety.